lymphatic system

• Lymphatic system


  Vital part of the body's immune and circulatory systems
• Lymphatic system


  • Maintains fluid balance
  • Defends the body against infections
  • Supports overall health
• Lymph


  A clear, watery fluid that circulates through the lymphatic system
• Lymph


  • Contains white blood cells (lymphocytes) and other immune system components
  • Collects waste products, bacteria, and other unwanted materials from body tissues
• Lymphatic vessels


  A network of thin tubes that carry lymph throughout the body
• Lymphatic vessels


  • Similar to blood vessels but transport lymph instead of blood
  • Start as small lymph capillaries in tissues and converge into larger lymphatic vessels
• Lymph nodes


  Small, bean-shaped structures located along the lymphatic vessels
• Lymph nodes


  • Act as filters, trapping bacteria, viruses, and other harmful substances
  • Contain lymphocytes that help fight infections
• Lymphoid organs


  • Spleen
  • Thymus
  • Tonsils and Adenoids
  • Bone Marrow
• Spleen


  Filters blood, removes old or damaged blood cells, and helps fight infections
• Thymus


  Where T-lymphocytes (a type of white blood cell) mature and become ready to fight infections
• Tonsils and Adenoids


  Trap pathogens from the air and food and help the body fight infections early
• Bone Marrow


  Produces blood cells, including lymphocytes, which are crucial for the immune response
• Fluid balance


  1. Returns excess tissue fluid to the bloodstream

  2. About 20 liters of plasma flow through capillaries into the body's tissues each day, 17 liters are reabsorbed by blood vessels, and 3 liters are returned to the blood via the lymphatic system
• Immune defense


  1. Produces and transports lymphocytes that attack and destroy bacteria, viruses, and other foreign substances

  2. Lymph nodes filter pathogens from the lymph before it returns to the bloodstream
• Absorption of fats


  1. The lymphatic system absorbs fats and fat-soluble vitamins from the digestive system and transports them to the bloodstream

  2. This occurs through specialized lymphatic vessels called lacteals in the small intestine
• The lymphatic system is essential for keeping our bodies healthy
• Lymphatic system


  Solves plumbing problem caused by leaky capillaries
• Lymphatic system


  • Actively scans for foreign invaders like bacteria and viruses
  • Reabsorbs leaked fluid and removes infectious agents
  • Activates specific immune defences for disease protection
• Components of the lymphatic system

  • Lymphatic vessels
  • Lymph
  • Lymph nodes
  • Spleen
• Lymphatic system


  • Extends throughout body like the cardiovascular system
  • Not a closed-loop system, unlike the cardiovascular system
• Lymph formation and flow

  1. Fluid leaks from blood vessel capillaries

  2. Fluid inside vessels called blood plasma

  3. Fluid outside vessels called interstitial fluid

  4. Fluid enters lymphatic capillaries through small gaps between endothelial cells

  5. Lymphatic capillaries -> lymphatic vessels -> lymphatic trunks

  6. Trunks drain lymph from various body parts

  7. Muscular contractions & organ movements push lymph

  8. Assisted by one-way lymphatic valves for directional flow
• Major lymphatic ducts


  • Right lymphatic duct
  • Thoracic duct (left lymphatic duct)
• Lymphatic cells


  • Lymphocytes: T cells, B cells, natural killer cells
  • Macrophages evolve from monocytes, destroy foreign cells
• Lymphatic tissues


  • Loose connective tissue containing lymphocytes
  • Mucosa-associated lymphatic tissue (MALT)
  • Tonsils
  • Peyer's Patches
• Lymph nodes


  • Dual purpose: cleanse lymph and store/produce T and B cells
  • Afferent vessels carry lymph into nodes
  • Flows from cortex to deeper medulla
  • Efferent vessels carry lymph away from nodes
  • Detects and reacts to foreign particles quickly
• Spleen


  • White pulp: rich in lymphocytes, activates immune response
  • Red pulp: macrophages destroy old RBCs, platelets, and pathogens
• Thymus


  • Functions as "nursery" for T cells, which mature here from lymphatic stem cells in bone marrow
• Body maintains homeostasis through dynamic regulatory systems, including blood
• Functions of blood


  • Transportation
  • Regulation
  • Protection
• Blood is involved in gas exchange: supplies oxygen, removes carbon dioxide
• Blood helps maintain pH balance through buffers and amino acids
• Formed elements


  Red blood cells, white blood cells, platelets
• Haematocrit


  Proportion of red blood cells in total blood volume
• Physical properties of blood

  • Comprises 8% of total body weight
  • Average volume: 4-5 litres, varies with body size and fitness
  • Slightly salty, with 0.9% sodium chloride
  • pH range: 7.35-7.45, average temp: 37°C
  • Colour varies with oxygen levels: bright red in arteries, darker in veins
• Plasma


  • Pale yellow, 90% water, 8% plasma proteins, 2% other elements
  • Contains proteins for lipid transport, blood pressure regulation, and clotting
  • Contains electrolytes like sodium, potassium, and calcium
  • Buffers like bicarbonate regulate pH
• Blood cell production


  1. Occurs in bone marrow

  2. Blood cells start as a haematopoietic stem cell, morphs into other types

  3. Influenced by hormones and growth factors

  4. Mature into red blood cells, white blood cells, or platelets

  5. Enter bloodstream through bone marrow
• Red blood cells (erythrocytes)

  • Primary function is gas exchange
  • Contain haemoglobin to carry oxygen to cells and remove carbon dioxide
  • Haemoglobin composition: globin (protein) and haem (iron molecule)
  • Oxygen and CO2 transport: oxygen binds to haemoglobin in lung capillaries, forming oxyhemoglobin, oxygen is released into tissues, replaced by CO2 binding to globin
  • RBC production (erythropoiesis) governed by kidneys via hormone erythropoietin
• White blood cells (leukocytes)

  • Serve as the body's infection fighters
  • Role in immune responses
  • Production doubles when infection detected
• Platelets (thrombocytes)


  • Part of the formed elements in blood
  • Crucial in haemostasis: blood clot formation and bleeding control